Theaetetus THEAET. Well, I do think so.

Socrates SOC. To which class, then, do you assign being; for this, more than anything else, belongs to all things?

Theaetetus THEAET. I assign them to the class of notions which the soul grasps by itself directly.

Socrates SOC. And also likeness and unlikeness and identity and difference?

Theaetetus THEAET. Yes.

Socrates SOC. And how about beautiful and ugly, and good and bad?

Theaetetus THEAET. I think that these also are among the things the essence of which the soul most certainly views in their relations to one another, reflecting within itself upon the past and present 186b in relation to the future.

Socrates SOC. Stop there. Does it not perceive the hardness of the hard through touch, and likewise the softness of the soft?

Theaetetus THEAET. Yes.

Socrates SOC. But their essential nature and the fact that they exist, and their opposition to one another, and, in turn, the essential nature of this opposition, the soul itself tries to determine for us by reverting to them and comparing them with one another.

Theaetetus THEAET. Certainly.

Socrates SOC. Is it not true, then, that all sensations which reach the soul through the body, 186c can be perceived by human beings, and also by animals, from the moment of birth; whereas reflections about these, with reference to their being and usefulness, are acquired, if at all, with difficulty and slowly, through many troubles, in other words, through education?

Theaetetus THEAET. Assuredly.

Socrates SOC. Is it, then, possible for one to attain “truth” who cannot even get as far as “being”?

Theaetetus THEAET. No.

Socrates SOC. And will a man ever have knowledge of anything the truth of which he fails to attain?

Theaetetus THEAET. How can he, Socrates?

Socrates SOC. Then knowledge is not in the sensations, but in the process of reasoning about them; for it is possible, apparently, to apprehend being and truth by reasoning, but not by sensation.

Theaetetus THEAET. So it seems.

Socrates SOC. Then will you call the two by the same name, when there are so great differences between them?

Theaetetus THEAET. No, that would certainly not be right.

Socrates SOC. What name will you give, then, to the one which includes seeing, hearing, smelling, being cold, and being hot?

Theaetetus THEAET. Perceiving. What other name can I give it?

Socrates SOC. Collectively you call it, then, perception?

Theaetetus THEAET. Of course.

Socrates SOC. By which, we say, we are quite unable to apprehend truth, since we cannot apprehend being, either.

Theaetetus THEAET. No; certainly not.

Socrates SOC. Nor knowledge either, then.

Theaetetus THEAET. No.

Socrates SOC. Then, Theaetetus, perception and knowledge could never be the same.

Theaetetus THEAET. Evidently not, Socrates; and indeed now at last it has been made perfectly clear that knowledge is something different from perception.

Socrates SOC. But surely we did not begin our conversation in order to find out what knowledge is not, but what it is. However, we have progressed so far, at least, as not to seek for knowledge in perception at all, but in some function of the soul, whatever name is given to it when it alone and by itself is engaged directly with realities.

Theaetetus THEAET. That, Socrates, is, I suppose, called having opinion.

Socrates SOC. You suppose rightly, my friend. Now begin again 187b at the beginning. Wipe out all we said before, and see if you have any clearer vision, now that you have advanced to this point. Say once more what knowledge is.

Theaetetus THEAET. To say that all opinion is knowledge is impossible, Socrates, for there is also false opinion; but true opinion probably is knowledge. Let that be my answer. For if it is proved to be wrong as we proceed, I will try to give another, just as I have given this.

Socrates SOC. That is the right way, Theaetetus. It is better to speak up boldly than to hesitate about answering, as you did at first. For if we act in this way, one of two things will happen: either we shall find what we are after, 187c or we shall be less inclined to think we know what we do not know at all; and surely even that would be a recompense not to be despised. Well, then, what do you say now? Assuming that there are two kinds of opinion, one true and the other false, do you define knowledge as the true opinion?

Theaetetus THEAET. Yes. That now seems to me to be correct.

Socrates SOC. Is it, then, still worth while, in regard to opinion, to take up again—?

Theaetetus THEAET. What point do you refer to?

Socrates SOC. Somehow I am troubled now and have often been troubled before, 187d so that I have been much perplexed in my own reflections and in talking with others, because I cannot tell what this experience is which we human beings have, and how it comes about.

Theaetetus THEAET. What experience?

Socrates SOC. That anyone has false opinions. And so I am considering and am still in doubt whether we had better let it go or examine it by another method than the one we followed a while ago.

Theaetetus THEAET. Why not, Socrates, if there seems to be the least need of it? For just now, in talking about leisure, you and Theodorus said very truly that there is no hurry in discussions of this sort.

Socrates SOC. You are right in reminding me. For perhaps this is a good time to retrace our steps. For it is better to finish a little task well than a great deal imperfectly.

Theaetetus THEAET. Of course.

Socrates SOC. How, then, shall we set about it? What is it that we do say? Do we say that in every case of opinion there is a false opinion, and one of us has a false, and another a true opinion, because, as we believe, it is in the nature of things that this should be so?

Theaetetus THEAET. Yes, we do.

Socrates SOC. Then this, at any rate, is possible for us, is it not, regarding all things collectively and each thing separately, either to know or not to know them? For learning and forgetting, as intermediate stages, I leave out of account for the present, for just now they have no bearing upon our argument.

Theaetetus THEAET. Certainly, Socrates, nothing is left in any particular case except knowing or not knowing it.

Socrates SOC. Then he who forms opinion must form opinion either about what he knows or about what he does not know?

Theaetetus THEAET. Necessarily.

Socrates SOC. And it is surely impossible that one who knows a thing does not know it, or that one who does not know it 188b knows it.

Theaetetus THEAET. Certainly.

Socrates SOC. Then does he who forms false opinions think that the things which he knows are not these things, but some others of the things he knows, and so, knowing both, is he ignorant of both?

Theaetetus THEAET. That is impossible, Socrates.

Socrates SOC. Well then, does he think that the things he does not know are other things which he does not know—which is as if a man who knows neither Theaetetus nor Socrates should conceive the idea that Socrates is Theaetetus or Theaetetus Socrates?

Theaetetus THEAET. That is impossible.

Socrates SOC. But surely a man does not think that the things he knows are the things he does not know, or again that the things he does not know are the things he knows.

Theaetetus THEAET. That would be a monstrous absurdity.

Socrates SOC. Then how could he still form false opinions? For inasmuch as all things are either known or unknown to us, it is impossible, I imagine, to form opinions outside of these alternatives, and within them it is clear that there is no place for fake opinion.

Theaetetus THEAET. Very true.

Socrates SOC. Had we, then, better look for what we are seeking, not by this method of knowing and not knowing, but by that of being 188d and not being?

Theaetetus THEAET. What do you mean?

Socrates SOC. We may simply assert that he who on any subject holds opinions which are not, will certainly think falsely, no matter what the condition of his mind may be in other respects.

Theaetetus THEAET. That, again, is likely, Socrates.

Socrates SOC. Well then, what shall we say, Theaetetus, if anyone asks us, “Is that which is assumed in common speech possible at all, and can any human being hold an opinion which is not, whether it be concerned with any of the things which are, or be entirely independent of them?” We, I fancy, 188e shall reply, “Yes, when, in thinking, he thinks what is not true,” shall we not?

Theaetetus THEAET. Yes.

Socrates SOC. And is the same sort of thing possible in any other field?

Theaetetus THEAET. What sort of thing?

Socrates SOC. For instance, that a man sees something, but sees nothing.

Theaetetus THEAET. How can he?

Socrates SOC. Yet surely if a man sees any one thing, he sees something that is. Or do you, perhaps, think “one” is among the things that are not?

Theaetetus THEAET. No, I do not.

Socrates SOC. Then he who sees any one thing, sees something that is.

Theaetetus THEAET. That is clear.

Socrates SOC. And therefore he who hears anything, hears some one thing and therefore hears what is.

Theaetetus THEAET. Yes.

Socrates SOC. And he who touches anything, touches some one thing, which is, since it is one?

Theaetetus THEAET. That also is true.

Socrates SOC. So, then, does not he who holds an opinion hold an opinion of some one thing?

Theaetetus THEAET. He must do so.

Socrates SOC. And does not he who holds an opinion of some one thing hold an opinion of something that is?

Theaetetus THEAET. I agree.

Socrates SOC. Then he who holds an opinion of what is not holds an opinion of nothing.

Theaetetus THEAET. Evidently.

Socrates SOC. Well then, he who holds an opinion of nothing, holds no opinion at all.

Theaetetus THEAET. That is plain, apparently.

Socrates SOC. Then it is impossible to hold an opinion of that which is not, either in relation to things that are, or independently of them.

Theaetetus THEAET. Evidently.

Socrates SOC. Then holding false opinion is something different from holding an opinion of that which is not?

Theaetetus THEAET. So it seems.

Socrates SOC. Then false opinion is not found to exist in us either by this method or by that which we followed a little while ago.

Theaetetus THEAET. No, it certainly is not.

Socrates SOC. But does not that which we call by that name arise after the following manner?

Theaetetus THEAET. After what manner?

Socrates SOC. We say that false opinion is a kind of interchanged opinion, 189c when a person makes an exchange in his mind and says that one thing which exists is another thing which exists. For in this way he always holds an opinion of what exists, but of one thing instead of another; so he misses the object he was aiming at in his thought and might fairly be said to hold a false opinion.

Theaetetus THEAET. Now you seem to me to have said what is perfectly right. For when a man, in forming an opinion, puts ugly instead of beautiful, or beautiful instead of ugly, he does truly hold a false opinion.

Socrates SOC. Evidently, Theaetetus, you feel contempt of me, and not fear.

Theaetetus THEAET. Why in the world do you say that?

Socrates SOC. You think, I fancy, that I would not attack your “truly false” 189d by asking whether it is possible for a thing to become slowly quick or heavily light, or any other opposite, by a process opposite to itself, in accordance, not with its own nature, but with that of its opposite. But I let this pass, that your courage may not fail. You are satisfied, you say, that false opinion is interchanged opinion?

Theaetetus THEAET. I am.

Socrates SOC. It is, then, in your opinion, possible for the mind to regard one thing as another and not as what it is.

Theaetetus THEAET. Yes, it is.

Socrates SOC. Now when one’s mind does this, does it not necessarily 189e have a thought either of both things together or of one or the other of them?

Theaetetus THEAET. Yes, it must; either of both at the same time or in succession.

Socrates SOC. Excellent. And do you define thought as I do?

Theaetetus THEAET. How do you define it?